1. Field of the Invention
The present invention relates to a wafer production method used in an etching process of a substrate, and more particularly, to a high density wafer production method for controlling a thickness of the wafer.
2. Description of the Prior Art
Silicon substrates are presently widely used in integrated circuits, optical electronics, microelectronics and microelectromechanical systems (MEMS). However, silicon substrates have shortcomings in many applications. For example, silicon substrates are crystal materials with crystal directions. Anisotropic etching processes are performed on silicon substrates by using a potassium hydroxide (KOH) solution. The etching speed of silicon in the direction  less than 100 greater than  and  less than 110 greater than  is far faster than that in the direction of  less than 111  greater than  for forming an inclined plan with 54.74xc2x0, creating a large waste of space. The waste of space becomes more serious with an increasing thickness of the silicon substrate.
Please refer to FIGS. 1 through FIG. 3, which are diagrams of print head structures of the prior art. FIG. 1 is disclosed in U.S. Pat. No. 6,019,907 xe2x80x9cForming refill for monolithic inkjet printheadxe2x80x9d. As shown in FIG. 1, the prior art inkjet printhead is formed on a silicon substrate 10 comprising two slots 11,12 for passing ink, two nozzle chambers 14,15 located on the surface of slots 11,12 for jetting the ink, and two resistors 16,17. The resistor 16 is located between the nozzle chamber 14 and the slot 11, and the resistor 17 is located between the nozzle chamber 15 and the slot 12 for heating the ink. The slots 11,12 form a refilling chamber 13 for decreasing the turbulent effect.
FIG. 2 is disclosed in U.S. Pat. No. 5,658,471 xe2x80x9cFabrication of thermal ink-jet feed slots in a silicon substrate.xe2x80x9d As shown in FIG. 2, the prior art inkjet printhead is formed on a silicon substrate 20 comprising slot 21 formed in the center of the substrate 20 for passing the ink, a dielectric layer 22 formed on the surface of the substrate 20, and two heaters 23,24 formed on the surface of the dielectric layer 22 for heating the ink. The dielectric layer 22 isolates the substrate 22 from the heaters 23,24. The structures shown in FIG. 1 and FIG. 2 are different, but they are manufactured by similar processes, and both waste space.
Please refer to FIG. 3, which shows a prior art inkjet printhead formed on a silicon substrate. As shown in FIG. 3, a standard cleaning process is performed on a silicon substrate with a width W1 and a thickness T1. A passivation layer 31 and a patterned passivation layer 32P are formed on a top surface and a bottom surface of a silicon substrate 30 for forming the surface patterns of slots 33,34. A distance between the slot 33 and the slot 34 is L1 and a distance between slots 33,34 and the wafer edge is L0. An etching process is performed on the silicon substrate by using potassium hydroxide (KOH) solution to form the structure of the slots 33,34, as shown in FIG. 3. The passivation layers 31,32P are composed of silicon oxide or silicon nitride.
The process of FIG. 3 applied in FIG. 1 and FIG. 2 for producing the inkjet printhead forms an inclined plane at 54.74xc2x0, creating a large waste of space. Additionally, the substrate needs sufficient space in L0 and L1 (as shown in FIG. 3) to glue an ink box (not shown). An inclined plane formed at 54.74xc2x0, and the space required for gluing the box lead to the creation of a large waste of space.
It is therefore a primary objective of the present invention to provide a method of high density wafer production that saves space.
Briefly, the claimed invention provides an etching method for high density wafer production used when etching a substrate for controlling a thickness of the wafer. The etching method forms a first patterned passivation layer and a second passivation layer on a top surface and a bottom surface, followed by performing a first etching process for simultaneously etching the substrate and the first passivation layer. After the first passivation layer is removed, a second etching process is performed to etch the substrate to a designated depth that is used to control the thickness of the wafer after the second etching process.
It is an advantage of the present invention that the etching method controls the thickness of the wafer and the size of slots for inkjet printhead and MicroElectroMechanical Systems applications.
These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.